Recent energy standards and regulations have been introduced in an attempt to reduce energy consumption by lighting. One common method is to reduce lighting levels when rooms are not occupied, typically achieved through the use of lighting control system with a motion sensor. Others methods include using active sensing to adjust lighting levels to compensate for light from natural and other sources, or using timers to reduce lighting levels during specific periods during the day.
Ambient light sensing systems typically use an external light sensor to measure light from natural sources and then determine the amount of overhead lighting needed to maintain predetermined or pre-programmed light levels. This sensor can either be wireless or wired into a lighting control system, but it is rarely ever incorporated into a bulb. If so, it has a shield to block the light sensor from the compensatory light source. The reason for this lies in the driver electronics; most modern lighting electronics output a very high frequency (greater than 10 kHz) or a near-constant DC voltage to maximize the period during with the light source emits light. This is especially true in light emitting diode (LED)-based bulbs. Any light sensor in the bulb, unless implemented with very fast controls or physically blocked from the compensatory light source, will be overwhelmed by the light output of the bulb itself and will likely not be able to accurately measure ambient light from other sources. Accordingly, a need exists for more effective ways to measure ambient light for controlling light sources.